1. Field of the Invention
The present invention relates to a magneto-resistance effect element which is configured such that a current is flowed in the direction perpendicular to the film surface thereof to detect the magnetization of the element and the magneto-resistance effect element and to a method for manufacturing the same.
2. Description of the Related Art
Recently, the miniaturization and the high density recording of a hard disk drive (HDD) is remarkably required and being progressed. In the future, it is promised to much develop the high density recording of the HDD. The HDD of high density recording can be realized by narrowing the recording track width. However, the amplitude of the magnetization relating to the recording, that is, the recording signal may be lowered as the track width is narrowed, so that it is required that the reproducing sensitivity of the MR head for reproducing the medium signal is enhanced.
Recently, a GMR (Giant Magneto-Resistance effect) head with a high sensitive spin valve film using the GMR film is employed. The “spin valve” film has such a structure as sandwiching a non-magnetic metal spacer layer between two ferromagnetic layers. The stacking layer component structure exhibiting the change in resistance may be called as a “spin dependent scattering unit”. The magnetization of one ferromagnetic layer (often called as a “pinning layer” or “fixed magnetization layer) is fixed by the magnetization of an anti-ferromagnetic layer and the magnetization of the other ferromagnetic layer (often called as a “free layer” or “free magnetization layer”) is rotated in accordance with an external magnetic field. With the spin valve film, the intended large magneto-resistance effect can be obtained when the relative angle between the pinning layer and the free layer is changed.
A conventional spin valve film is formed as a CIP (Current In Plane)-GMR element, a CPP (Current Perpendicular to Plane)-GMR element and a TMR (Tunneling Magneto-Resistance) element. With the CIP-GMR element, a sense current is flowed along the film surface of the spin valve film. With the CPP-GMR element or the TMR element, a sense current is flowed in the direction perpendicular to the film surface thereof.
With the element which is utilized by flowing the sense current in the direction perpendicular to the film surface, the spacer layer is made of an insulating layer in the TMR element and of a metallic layer in the CPP-GMR element.
Herein, a metal CPP-GMR element of which the spin valve film is made of a metallic layer has a smaller change in resistance to render the detection of small magnetic field difficult. In this point of view, in References 1 and 2, such an attempt is made as inserting a layer made of at least one selected from the group consisting of Cr, V, Ta, Nb, Sc, Ti, Mn, Cu, Zn, Ga, Ge, Zr, Hf, Y, Tc, Re, Ru, Rh, Ir, Pd, Pt, Ag, Au, B, Al, In, C, Si, Sn, Ca, Sr, Ba, O, N and F in the fixed magnetization layer of the free magnetization layer composing the spin dependent scattering unit, thereby enhancing the variation ratio in resistance of the CPP-GMR element and thus, thereby enhancing the magneto-resistance effect of the CPP-GMR element.
On the other hand, a CPP element with an oxide layer containing current confining paths in the thickness direction thereof, which is called as an “NOL (nano-oxide layer)”, is proposed (refer to Reference 3). With the CPP element, both of the element resistance and the MR ratio can be increased due to the current confined path (CCP) effect. Hereinafter, the element is called as a “CCP-CPP element”.
[Reference No. 1] JP-A 2003-133614 (KOKAI)
[Reference No. 2] JP-A 2003-60263A (KOKAI)
[Reference No. 3] JP-A 2002-208744 (KOKAI)
In the CCP-CPP element, it is required to much enhance the sensitivity of the CCP-CPP element. The sensitivity can be defined as the MR ratio.